Is the lifespan for silnylon limited? I am wondering if perhaps my rain chaps no longer are waterproof (actually I kind of wonder if they ever really were waterproof, but I digress.) I'm curious, however, if silnylon stops being waterproof after a while.

Yes. Other than Shield from Thru-Hiker, every retail DIY silnylon that I have tested is less than the threshold for rain proof at 1,500 mm when new. It only gets worse since wet flex degrades the coating; it becomes less waterproof with each use. The degradation curve is hockey stick shaped. It starts degrading fast and then slows down.

The good news is that it is an easy problem to solve. Just paint one side with “1:3 slurry of Silicone and mineral spirits” to rejuvenate the coating.

> How do you guys get the slurry to mix well?Its very, very hard to do, especially with the hardware store cartridges.And while you are mixing vigorously, the trace water in the solvent is making the silicone start curing.

I haven't done this yet, tents are still new enough, but I've read a few people here say to use a drill with a clothes hanger wire bent to form a sort of whisk shape. Makes sense to me, same idea as a blender vs using a mortar/pestle to make pesto... good luck ever getting the pesto smooth with mortar and pestle, easy with a power tool, I know, I tried that for a while (pesto by hand that is, same idea, oily thing mixing in with something you want to blend perfectly into the oil). Power whisk type thing is what I would do in this case, then add in a bit more mineral spirits and whisk again with drill if it starts setting.

This is one reason I decided not to use silnylon fabric on my recent backpack project, I was debating it, but opted for very nicely coated 70d, which, if you add in the extra weight of coating again silnylon, starts looking better and better all the time. Keep in mind there's a huge range of coating thickness and quality for pu coated nylon too.

It can be VERY simple...Get a small can , I used tuna cans but a cut down soda can will do, a small paint brush, paint thinner and the silicone.Put a blob of silicone in the can. add a little bit of paint thinner , mix in with your paint brush. Add a bit more thinner, mix in and keep doing it till you get the consistency you like.Thick olive oil is what I aim for.Takes me well under a minute to do...You can see that at the start of this video :http://www.youtube.com/watch?v=mYjOkxR4sgc&list=UU0PuLUKvG7Fxxex5BMVK4vw&index=6&feature=plcpBTW, I do dozens of tents a year so if I thought there was a faster or easier way I would do it...Franco( I just seam sealed a Notch. Used about 2/3 of an ounce of silicone. I have now a small plastic bowl from which the silicone can be peeled off from when dry so I keep re-using that)